1. Field of the Invention
This invention relates to a multi-cylinder engine, and more particularly to a multi-cylinder engine wherein a crankshaft is provided on which a plurality of crank journals are individually rotatably supported through main metal bearings on a plurality of bearing portions provided on a crankcase and crankpins to which major end portions of connecting rods are integrally provided and are connected for pivotal motion. The crankpin oil paths are provided for supplying lubricating oil between the major end portions of the connecting rods and the crankpins.
2. Description of Background Art
Conventionally, in a multi-cylinder engine disclosed, for example, in Japanese Patent Laid-open No. 2002-213302, the crankpin oil paths are provided in a crankshaft in such a manner as to connect a plurality of crank journals provided on the crankshaft and crankpins.
Incidentally, a metal bearing is interposed between a crank journal of a crankshaft and a bearing portion of a crankcase. In the conventional multi-cylinder engine described above, in order to establish communication between the crankpin oil paths provided between crank journals and the crankpins and the oil supply paths provided in bearing portions on which the crank journals are supported, annular oil grooves are provided at central portions of metal bearings in the axial direction. Therefore, the area of the metal bearings for supporting a load decreases and the load capacity of the metal bearings decreases. Accordingly, in order to sufficiently assure the load capacity of each metal bearing, it cannot be avoided to set the width of the metal bearings, that is, the length of the crank journals in the axial direction, comparatively great. This gives rise to an increase in the scale and an increase in the weight of the engine in the axial direction of the crankshaft.